REM Sleep Disorder Doubles Risk of Parkinson's Disease

People with symptoms suggesting rapid eye movement sleep behaviour disorder, or RBD, have twice the risk of developing mild cognitive impairment (MCI) or Parkinson's disease within four years of diagnosis with the sleep problem, compared with people without the disorder, a Mayo Clinic study has found.

One of the hallmarks of rapid eye movement (REM) sleep is a state of paralysis. In contrast, people with rapid eye movement sleep behaviour disorder, appear to act out their dreams when they are in REM sleep. Researchers used the Mayo Sleep Questionnaire to diagnose probable RBD in people who were otherwise neurologically normal. Approximately 34 per cent of people diagnosed with probable RBD developed MCI or Parkinson's disease within four years of entering the study, a rate 2.2 times greater than those with normal rapid eye movement sleep.

"Understanding that certain patients are at greater risk for MCI or Parkinson's disease will allow for early intervention, which is vital in the case of such disorders that destroy brain cells. Although we are still searching for effective treatments, our best chance of success is to identify and treat these disorders early, before cell death," says Brad Boeve, a Mayo Clinic neurologist.

Previous studies of Mayo Clinic patients have shown that an estimated 45 per cent of people who suffer from RBD will develop a neurodegenerative syndrome such as mild cognitive impairment or Parkinson's disease within five years of diagnosis.

"This study is the first to quantify the risk associated with probable RBD in average people, not clinical patients, and it shows that we can predict the onset of some neurodegenerative disorders simply by asking a few critical questions," says lead author Brendon P. Boot.

• MCI is an intermediate stage between the expected cognitive decline of normal aging and the more pronounced decline of dementia. It involves problems with memory, language, thinking and judgment that are greater than typical age-related changes.

• An estimated 500,000 Americans suffer from Parkinson's disease, which is characterised by tremor or shakiness, stiffness of the limbs and trunk, slowness of movement, and impaired balance and coordination.